We propose to studythe electrical activity of neurons by continuous intra- and extracellular techniques in Aplysia, a marine gastropod, while the isolated tissue are continuously cultured in nutrient medium in vitro. The endogenously active neurons of the abdominal ganglion will be studied for their long term rhythmic, circadian, behavior during the appropriate experimental manipulation with light, chemical or specific stimulation of nerves. The short-term adaptive changes in synaptic potentials, depression or facilitation, between identified neurons will also be studied in culture. This will also be pursued over days and weeks to study the retention of specific synaptic changes. The eye of Aplysia, which has a precise circadian rhythm will also be studied in culture, either attached to the cerebral ganglion or isolated. We will look for evidence of the synthesis, release and action of newly synthesized products by the administration of labelled precursor molecules to the eye in pursuing the hypothesis that the eye secretions are important in coupling the rhythmic activity of th eye to other physiological processes in the animal. We will also study the neuronal mechanism that are responsible for the rhythmic activity of the eye.